1796/97 Richard Haywood 'verge discovery'

Discussion in 'European & Other Pocket Watches' started by John Matthews, Oct 27, 2018.

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  1. gmorse

    gmorse Registered User
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    Hi John,

    It looks as though the shaft of the minute hand could be original, so putting a new arrowhead on it would not be too difficult.

    Regards,

    Graham
     
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  2. John Matthews

    John Matthews Registered User
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    Sep 22, 2015
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    Noted ...

    Over the last few days I have been incrementally adjusting the Tompion regulator in an attempt to bring it closer to time. The end result is that having rotated the index dial one revolution the watch is now losing ~5 minutes in 24 hours. In the pendant up position, it lost 1 minute in 5 hours this morning – a significant improvement from the 40 minutes in 24 hours at the start of this process. As I indicated earlier, I'm not looking to achieve an accurate timepiece; I am perfectly happy with this result and don't intend to make any further adjustment.

    However, I would like to understand the performance after I re-assembled the watch, so here is my current understand, which I provide for comment and correction …

    As purchased the chain was broken and, therefore, I have no measure of the accuracy of the time-keeping when it was previously working. What is known from the service, is that there was significant end shake and that the amplitude of the balance oscillation was very small and the rate very quick when the watch was first re-assembled. By adjusting the position of the follower I was able to reduce the end shake and achieve a more reasonable oscillation of the balance, both in terms of amplitude and rate.

    Following the statements “In a verge watch the balance spring does not take complete control” and a 'factor which tends to neutralise the balance spring is the escapement action”, Gazeley describes how the adjustment of the end shake may be used to correct timing (Clock & Watch Escapements p.116). By reducing the end shake, and thereby deepening the escapement depth, the timing of the watch will be slowed. So this is effectively what I did.

    When I re-assembled the watch, I believe that I positioned the hairspring on the balance as it was originally. I also pinned the spring at approximately the same point as previously. I positioned the index pins of the regulator close to the midpoint of the Tompion rack. Although, I have not removed the balance to confirm, by counting the teeth of the pinion and rack, I am confident that the index pins will have been moved very close to the limit of their adjustment. My estimate is that I have moved the index pins by between 5 and 10 mm.

    At this point, if I wished to improve the timing further, I would need to follow

    So, if I understand correctly, I would need to re-pin the hairspring so that it was ~ 7mm shorter and adjust the beat by rotating the position of the hairspring on the shaft. When re-fitting the balance I would bring the index pins back to a mid-point position.

    Is my understanding correct?

    John
     
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  3. gmorse

    gmorse Registered User
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    Hi John,

    Yes, quite correct. Pre-balance spring verges were almost entirely dependent on the power of the mainspring to regulate them, and that still has a significant influence on the later ones, even with the benefit of balance springs.

    Regards,

    Graham
     
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  4. John Matthews

    John Matthews Registered User
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    Graham - understood thanks to all your help ...

    John
     
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